1. Field
The present application relates to methods and apparatus for decoding frame packet data in a communication system and, more particularly, for incremental redundancy decoding of broadcast channel information within a wireless communication frame.
2. Background
In particular wireless communication systems, such as those operating according to the mobile broadband wireless access (MBWA) or IEEE 802.20, certain broadcast channel packets are encoded using a low effective coding rate to ensure reliable decoding of system parameters. In one example, the packets are convolutionally encoded (e.g., 1/3 convolutional encoding rate), channel interleaved, repeated, and quadrature phase shift keying (QPSK) modulated. These modulated symbols are transmitted over a predetermined P number of superframes in a preamble (e.g., a first symbol or beginning sequence of symbols) of each superframe. A typical number used for P is sixteen (16) superframes. The symbols may be an orthogonal frequency division multiplexed (OFDM) symbols or any other suitable communication system methodology. An example of these broadcast channel packets includes a pBCH0 packet, which is a broadcast channel that carries deployment specific parameters to be communicated to a mobile receiver (e.g., deployment-wide static parameters like cyclic prefix duration, number of guard carriers, and the superframe index) according to the IEEE 802.20 standard.
It is noted that in the IEEE 802.20 standard, in particular, pilot phase information, which is used for initial acquisition, is also contained in the preamble of each superframe and carries pseudorandom noise (PN) codes and overhead channels, such as an acquisition channel ACQCH and a broadcast channel OSICH. By obtaining the pilot phase information from these channels, the start of a pBCH0 packet may be determined where the relationship of pilot phase mod pBCH0 transmission period (P=16, for example)=0. In one example, the pilot phase information may be a number between 0 and 4,096. Thus, for example, for those pilot phase numbers divisible by P (e.g., 16) without a remainder, it may be known that this is the start of a pBCH0 packet.
In certain known receivers, the receiver is configured to wait until the start of the pBCH0 packet before receiving the modulation symbols. Once the start of a pBCH0 packet is determined, such receivers receive all the modulation symbols transmitted over the P (16) superframes and then combine them, accordingly. With such receivers, however, the receiver must wait for at least 16 superframes before starting demodulation and decoding of the pBCH0 packets. Thus, the start of demodulation and decoding of further broadcast channel packets, such as a pBCH1 packet, which contains information such as forward link hopping patterns, pilot structure, control channel structure, and transmit antennas, and must be demodulated and decoded after demodulation and decoding of pBCH0 is delayed.